FEBRUARY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
a general correlation of observed steam-film coefficients by the Nusselt equation, for other than very short tubes, requires a more complex relation than that provided by a constant correction factor. Badger, Monrad, and Diamond (1) presented data for diphenyl condensing on a vertical tube. These data deviated considerably from those predicted by the Nusselt theory; this deviation was explained by the turbulence in the condensate film. Kirkbride (6) measured film thicknesses for hydrocarbon oils and water flowing down a vertical tube, and stated that film thicknesses should check the Nusselt theoretical thickness for viscous flow over a range of W / p D up to about 1,800. He was able to correlate satisfactorily the data of Badger, Monrad, and Diamond, as well as some other data, by the equation: h.
(&)”*
= 0.0084
(5)”‘
He stated that for values of W/pD below 1,800, the constant and exponent of this term should theoretically be 1.35 and -l/8, respectively, since the film was in viscous flow below this value. It is possible to use these equations for design. However, the value of W is used to determine the amount of heat transferred and thus the value of the observed coefficient. Therefore, h. is to a certain extent plotted against itself in the correlation. Furthermore, the value of W is not directly known to the designer unless At, can be fixed independently. It would seem more desirable to have a term involving At, used in the equation, since this can be predicted more readily than
W.
215
coefficient was the difference between the steam temperature and the integrated average tube-wall temperature. The latter was obtained by plotting the tube-wall temperature distribution along the length of the tube, integrating the area under the curve and dividing by the length of the tube to give the average temperature. This procedure was necessary because of the marked variations in the wall temperatures along the length of the tube. Such variations were also observed by Hebbard and Badger (4).
Steam-film coefficients for a 2-inch 0. d., 20-foot long vertical tube are correlated by means of the coordinates, h,
(k:;2g)1J8
and
kat, .
Other data for tubes 8 feet and 12 Ph feet long are also correlated on the same basis and found to deviate from those for the 20-foot tube by a factor of L1I2. No apparent break in the curve, indicating viscous and turbulent flow, could be observed, though it is believed that turbulence must occur over at least part of the tube. Therefore, turbulence in the steam condensate film apparently does not control the rate of heat transfer, within the range of these experiments.
Experimental Apparatus The data for this investigation were obtained in an experimental long-tube vertical evaporator equipped with a single 2-inch 0. d., 20-foot long copper tube. The apparatus is described in an accompanying paper (7). Steam condensed on the outside of the tube, which was provided with tube-wall thermocouples installed by the method of Hebbard and Badger (3). The condensed steam was collected in drip tanks, and the amount of condensate was used as a measure of the heat transfer. The steam temperatures were calculated from the readings of a mercury manometer and checked by thermocouples placed in the steam jacket. The temperature drop used to calculate the heat transfer
1
1
Correlation of Steam-Film Coefficients
An attempt was first made to correlate tlie data with the Nusselt relation. Although very scattered, the data produced a band of approximately the theoretical slope of - l / p , but with an intercept somewhat higher than the theoretical. At the same time the coefficients were definitely lower than those of Hebbard and Badger. When plotted by the relation derived by Kirkbride, the data produced a band of points with a continued negative slope somewhat less - than that predicted for viscous flow, extending over values of W/pD from 200 to 3,000. HEBBARD AND BADGER, 1 2‘TUBE 1 I dX FRAGEN, 8’TUBE I I / I l l I There was no noticeable break a t W/pD = 1,800, though the slope decreased slightly beyond W / p D = 1,000; this indicated that if the range were extended, it would acquire a positive slope at sufficiently high values of W/pD. T h e d a t a were t h e n plotted, using the same ordinate as that of Kirkbride but another dimensionless group, IcAtJpA, as the abscissa. This gave a band of points with a slightly greater negative slope and with no noticeable break, within the range of the data. FIGURE1. CORRELATION OF ’ STEAM-FILM COEFFICIENTS
,
INDUSTRIAL AND ENGINEERING CHEMISTRY
216
TABLE I.
Run No.
B
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
20
C
21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 1 2 3 5 6 7 9 10
11
D
12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 35 37 38 a9 40 41 42 43 44 45 46 47 1 2 3 4 5
SteamFilm Cpeffioient B.t.u.1 AT. Film (hr.) (sa. Temp.,'F. ft.)('F.) Tav. hs At8 Stroebe, Baker, and Badger 20-Foot Tube 168.67 1428 1B:bz 911 6:44 X 10-8 164.00 18.32 882 8.56 180.06 25.85 900 13.76 187.51 746 21.97 179.44 9.99 1000 3.29 168.86 7.78 4.01 971 1.60 159.37 952 3.66 8.67 166.43 941 174.17 13.23 5.91 6.62 1070 5.78 165.98 10.28 21.93 180.16 743 867 24.72 12.22 187.94 13,22 745 26.89 187.09 3.18 1362 13.25 164.95 10,49 169.80 830 4.51 3.02 7.18 166.38 862 164.39 1455 1.14 2.75 173.04 6.01 13.59 759 4.37 796 162.70 1.78 11.76 5.08 170.06 814 16.83 7.64 175 80 795 27.17 13.82 905 191.89 6.79 2.86 961 166.34 13.42 5.97 834 173.73 10.49 4.53 170.02 775 15.70 869 7.12 176.58 844 24.08 11.50 188.41 865 8.86 18.88 180,78 1018 14.79 27.89 196.94 17.56 7.91 175.36 775 11.37 23.47 184.53 901 24.07 890 11.60 184.34 6.34 1231 2.68 167.08 12.89 852 5.73 173.80 17.35 8.15 844 180.93 900 11.68 23.42 188.85 699 2.61 6.53 161.43 11.98 5.14 834 169.03 7.95 17.61 729 175.38 24.09 789 11.52 183.25 8.31 3.46 969 165.86 15.14 831 6.71 172.72 21,56 10.06 796 179.67 25.58 11.74 844 177.79 1.09 ... 4330 9.52 4.96 977 14.86 7.95 1060 22.88 12.70 932 30.78 17.90 844 210.03 22.60 12.05 892 197.41 1043 8.44 4.28 190.61 8.31 15.63 905 197.54 22.96 12.80 822 204.02 22.09 906 17.05 210.93 8,93 963 4.51 190.63 4.90 1052 2.43 188.09 15.32 8.16 914 197.50 20.59 11.50 852 204.86 1009 20.52 11.48 204.80 25.66 15.10 1031 212.40 6.38 3.14 944 186.86 12.23 932 6.42 195.52 17.39 9.63 1070 20.80 33.43 978 2.74 5.60 1069 6.64 12.81 885 17.88 9.78 964 20.45 33.71 926 24.43 14.08 956 8.87 4.48 1010 20.98 11.72 1060 4.45 1050 8.80 15.01 8.01 950 11.52 1079 20.48 30.05 18.22 1031 6.56 12.68 952 9.38 17.16 1080 23.78 13.70 1100 10.29 5.19 879 14.87 7.94 1015 11.49 1113 20.40 8.09 15 09 999 996 12.75 6.14 3.12 6.36 4.45 8.80 7.55 14.11 11.01 19.48 2.80 5.25 4.39 8.64 208.44 1170 3.28 1.88 215.54 1101 10.44 6.27 221.49 1070 17.17 10.95 222.00 1042 15.95 10.09 229.08 1038 22.08 14.68 I
STE-4M-FILM
VOL. 31, NO. 2
COEFFICIENTS SteamFilm Cueffioient
1 342 0.898 0.784 0.775 0.666 0.950 0.958 0.904 0.864 1.020 0.662 0.743 0.640 1.308 0.775 0.820 1.400 0.694 0.775 0.761 0.720 0.765 0.913 0.765 0.720 0.784 0.765 0.765 0.837 0.703 0.788 0.828 0.846 0.779 0.743 0.770 0.680 0.784 0.662 0.689 0.922 0.770 0,707 0.760 I
o:ii5
0.872 0.747 0.658 0.734 0.886 0.743 0.658 0.707 0.814 0.904 0.762 0.678 0.859 0.796 0.814 0.774 0.859 0.734 0,922 0.738 0.779 0.725 0.752 0.855 0.845 0.886 0.779 0.859 0 792 0.796 0.873 0.864 0.743 0.833 0.890 0.823 0.828 0.841 0.833 0.850 0.931 0.975 0.948 1.400 0.846 0.796 0.774 0.778 I
Av. Fi!m Temp., F. Run No. Tav. Stroebe, Baker, D 6 236.06 7 218.10 8 226.60 9 208.28 10 212.18 11 212.69 12 218.69 13 228.78 14 235.94 15 222.02 16 215.34 17 211.54 18 208.33 19 222.80 20 229.30 21 236.57 22 215.30 23 211.62 24 219.34 25 226.36 26 215.49 27 222.56 28 229.71 29 214.93 30 226.51 31 236.08 E 1 167.25 2 176.28 3 184.08 4 192.26 5 213.79 6 223.81 7 234.63 F 1 171.21 2 182.34 3 194.08 4 178.65 5 188.32 6 197.15 78 9
SEH 3A1
3B1 5A1 5B1
lOAl
lOBl 13A1 13B1 SEU 3A1 3B1 5A1 5B1 lOAl lOBl l3Al 13B1 SEF 3A1 3B1 5A1 5B1 lOAl lOBl 13A1 13B1 SCH 3A1 3B1 5A1 5B1 lOAl lOBl 13A1 13B1
220.27 227.92 241.11
B.t.u:/
(hr. (sq ft.)(OF.j ha Ats and Badger 20-Foot 960 29.13 1028 14.21 1027 19.28 1481 3.48 1183 6.42 1000 10.48 950 13.48 894 23.18 941 28.36 931 16.37 1174 9.40 965 6.93 979 3.98 1038 16.89 1080 22.09 696 27.28 1209 9.63 1194 6.99 1115 12.68 1118 18.16 969 9.76 1129 15.54 1024 21.21 1149 10.79 1167 17.89 1031 27.35 1100 5.49 873 15.39 845 23.46 1037 27.47 1288 13.17 1153 23.90 1192 32.77 722 6.90 1117 15.72 975 22.33 1210 10.77 934 14.05 946 17.23 1221 9.92 1173 14.95 1126 18.94
kAtts Tube (Cont'dl 20.42 8.78 12.51 19.95 3.79 6.21 8.31 15.38 19.65 10.32 5.66 4.07 2.29 10.10 14.70 19.01 5.74 4.11 7.86 11.82 5.90 9.87 14.18 6.46 11.68 21.70 2.32 6.97 11.36 13.98 7.87 15.30 16.41 3.01 7.49 11.55 4.96 7.52 9.14 6.19 9.85 13.60
3B1 5A1 5B1 lOAl
1.168
0.917 0.774 0.716 0.648 0.662 0.694 0.900 0.747 0.770 0.770 0.778 0.488 0.922 0.922 0.836 0.819 0.720 0.836 0.738 0.877 0.855 0.725 1.038 0.787 0.734 0.873 0,993 0.850 0.841 0.671 0.935 0.814 1.090 0.792 0.778 0.912 0.882 0.778
Data of Hebbard and Badger, 12-Foot Tube 242.05 12.17 8.8 242.01 12.17 8.8 240.93 13.97 10.01 240.94 13.95 10.00 239.37 12.61 17.73 239.24 17.71 12.60 238.09 19.78 13.90 13.92 238.06 19.80
235.07 236.04 233.94 233.66 229.78 229.61 228.85 228.72
1898 1736 1440 1425 1473 1472 1426 1430 1175 1168 1153 1130 1044
1100
1086 1053
25.70 23.85 27.95 28.51 36.27 36.47 38.70 39.20
~
17.10 16.53 19.08 19.41 24.10 24.30 25.60 25.90
SCE
SCD 3A1
0.680
0.778 0.756
191.19 191.23 190.56 190.74 189.23
1682 1471 1426 1400 1296
4.49 4.62 6.70 6.72 9.07
2.29 2.36 3.39 3.40 4.54
0.643 0.636 0.625 0.623 0.585 0.615 0.609 0.692 0.837 0.867 0.768 0.747 0.713 0.701 0.713 0.705 0.693 0.696 0.722 0.720 0.703 0.700 1.100 0.961 0.935 0.918 0.855
,
FEBRUARY, 1939
INDUSTRIAL AND ENGINEERING CHEMISTRY
217
TABLEI. STEAM-FILM COEFFICIENTS (Continued)
Av. Film Temp.,'F.
Run No.
Tw.
SteamFilm Cqeffioient B.t.u.7 (hr. (sq ft.)toF.j ha
kAt,
At,
h~(&)"~L1/3
R u n No.
Data of Hebbrtrd and Badger, 12-Foot Tube (Cont'd)
SCD lOBl
13A1 13B1 S A E 3A1 3B1 3c2 3c3 !C4 oAl 5B1 6A2 5B2 lOAl lOBl 10A2 10B2 12A1 12B1 SAD 3A1 8B1 5A1 5B1 lOAl lOBl 13B1 S A C 3A1 3B1 SA1 5B1 lOAl lOBl 12A1 12B1
191.25 188.76 188.82 201.32 201.28 200.90 201.82 201.20 198.18 198.16 198.21 198.00 193.71 193.89 193.57 193.88 193.17 193.26 185.52 185.56 182.68 182.87 179.65 179.43 179.17 171.27 171.20 169.28 169.10 166.73 166.66 166.05 166.12
1282 1227 1226 1097 1119 1070 1042 1035 1001 980 935 924 945 1035 906 926 953 953
1232 1290 1048 1051 1012 99 1 944 932
8.93 9 94 9.90 21.37 21.26 21.71 21.08 21.49 27.83 28.39 27.85 28.12 36.86 36.68 37.66 37.51 38.43 38.43 16.96 16.88 22.72 22.09 28.82 29.14 30.49 10.08 i n .. 1.5 ~. ~~
14.09 14.05 18.54 18.61 20.09 20.20
4.54 4.95 4.93 11.68 11.60 11.80 11.58 11.74 14.88 15.15 14.89 15.00 19.09 19.00 19.50 19.40 19.85 19.85 8.26 8.23 10.82 10.55 13.41 13.55 14.20 4.38 4.42 6.04 6.04 7.81 7.85 8.43 8.46
BR
0.838 0.810 0.810 0.686 0.700 0.672 0.654 0.648 0.634 0.623 0.592 0.586 0.610 0.668 0.587 0.599 0.616 0.616 0.706 0.696 0.696 0.706 0.714 0.626 0.608 0.883 0.925 0.760 0.762 0.745 0.730 0.695 0.686
BL
BR
BP
CK CL
Data of Fragen, 8-Foot Tube AK
AL
AR
130 lZo 140 220 230 240 320 321 330 340 341 420 430 440 120 130 140 220 221 230 240 330 340 420 430 110 111 120
.130
AP
AD
BK
140 210 211 230 240 310 320 110 111 112 120 130 140 220 221 240 310 311 331 340 410 430 441 120 140 150 220 240 251 320
185.0 177.0 193.4 176.6 184.2 191.0 174.9 174.9 182.1 189.4 189.4 175.2 181.1 187.8 191.1 199.5 208.6 190.4 190.4 197.5 205.0 196.1 202.8 189.6 196.3 196.0 196.0 205.4 215.0 224.6 193.2 193.0 212.9 222.7 195.1 203.6 219.7 219.7 219.7 228.1 234.5 244.5 228.0 228.0 243.3 218.8 218.8 235.5 242.6 219.1 234.5 241.7 174.0 189.0 203.5 173.4 186.4 198.9 174.0
2285 1630 1740 1350 1525 1440 1290 1340 1460 1275 1340 1565 1390 1345 1595 1960 1920 1820 1565 1530 1510 1340 1370 1545 1645 2530 2280 1945 1935 2160 1900 2010 1700 1620 1760 1610 2235 2020 2120 1780 1370 1480 1325 1815 1570 2420 2070 1775 1635 2090 1830 1650 1885 1620 1720 1875 1390 1450 1945
11.2 5.9 13.1 10.1 13.36 18.0 11.15 11.15 14.6 20.8 20.8 10.6 16.6 22.8 9.0 10.2 11.2 10.3 10.3 14.3 19.1 17.0 22.4 12.3 16.7 3.6 3.5 7.7 9.9 12.8 4.9 4.9 15.3 19.3 5.9 11.7 3.3 33.3 .3 7.9 14.7 17.0 99.30 .3 19.4 3.9 3.9 14.5 20.8 4.1 16.7 22.7 5.9 11.1 13.1 7.4 15.8 22.7 6.2
2.69 5.45 6.76 4.59 6.43 9.13 5.00 5.00 6.93 10.40 10.40 4.77 7.81 11.30 4.57 5.50 6.45 5.20 5.20 7.60 10.70 8.95 12.40 6.15 8.81 1.84 1.84 4.34 5.95 8.25 2.52 2.52 9.10 12.28 3.08 6.50 2.08 2.05 2.05 5.21 10.05 12.52 6.14 6.14 14.18 2.41 2.41 10.10 15.10 3.91 11.5 16.4 2.63 5.55 7.27 3.27 7.66 12.2 2.77
0.895 1.310 0.922 0.772 0.842 0.770 0.742 0.772 0.815 0.685 0.719 0.900 0.778 0.730 o,855 1.014 0.956 0.975 o,798 0.837 0.764 0.702 0.700 0.832 o.863
351 440 450 120 140 160 240 260 320 340 360 440
~
440 132 140 320 340 440 122 143 661 146 642
Av. Film Temp.,'F.
Tav.
SteamFilm Coe5oient B.t.u.) (hr.)(sq. ft.)(OF.) ha
At8
Data of Fragen, 8-Foot Tube 198 2 1575 23.0 1390 23.1 183 1 196.3 1400 27.3 191.6 1852 4.8 210.9 2100 9.5 229.1 1800 14.7 1800 12.5 209.8 227.2 1615 19.2 190.5 1745 7.4 207.1 1595 17.5 223.6 1470 26.3 209.7 1460 23.4 211.7 6.8 12.4 226.3 19.2 243,3 210.6 8.6 224.7 15.9 223.7 18.2 239.5 2500 6 6 249.5 1955 10.9 1800 6.6 229.0 244.6 1640 16.4 243.7 1535 18.2 180.8 1970 1.8 200 1 1925 4.6 213.5 1315 19.4 215.1 1905 6.0 213.5 1730 9.8
kits
(Cont'd) 12.3 11.05 14.35 2.44 5.57 9.75 7.27 12 52 3.73 10.00 16.85 13.60 4.00 8.00 14.01 5.02 10.25 15.30 4.69 8.20 4.37 12.10 13.20 0.85 2.49 11.52 3.61 5.84
'/aL'/l
0.817 0.770 0.733 0.990 1 033 0.823 0.888 0.747 0.937 0.798 0.687 0.721
1.095 0.840 0.823 0.710 0.668 1.106 0.991 0.639 0.922 0.843
The data of Hebbard and Badger were next correlated with the same relationship. This produced a band of points of approximately the same slope but definitely higher. Since the tube used for their experiments was 12 feet long and 1 inch 0. d., the indication would be that the coefficients were also a function of the length of the tube. Accordingly, the data of Fragen (9) on steam-film coefficientsfor a tube '/s inch 0. d. and 8 feet long were correlated, using the same coordinates. This gave a band of points, also of approximately the same slope, but with higher values than either the present data or those of Hebbard and Badger. It was found that by multiplying the ordinate in each case by L1j 2 , all three sets of data fell into a single band, the result of which is shown in Figure 1. The data can be represented, within a deviation of *20 per cent, by a line whose slope is roughly -0.2, and this line can be expressed by the equation
1,322 0.982 1.195 0.936 1.010 1.009 1.070 0.831 0.761 0.925 0.820 1.064 0.963 1.008 0.818 0.614 0.639 0.608 0.835 0.679 1.152 0.987 0.792 0.993 0.713 0.818 0.718 1.098 0.875 0.877 0.806 0.758 0.753 1.127
h, (&)'I3
L1J2 = 0.29
The data are given in Table I. An unsuccessful attempt was made to incorporate the diameter as well as the length of the tube into the correlation. However, since the observed coefficient is an over-all coefficient for the entire tube, and since this coefficient will vary with the average thickness of the condensate film, it would seem that the tube length would be of considerable significance, whereas the effect of tube diameter within the range of the three sets of data would be negligible. Therefore it was considered that a simple function of tube length was most suitable for the correlation of the data. The data presented here were obtained in conjunction with another investigation (7) whose primary concern was the determination of the film coefficients on the inside of the tube. The steam used was from the university mains, and probably was not absolutely pure but contained small and varying amounts of air and oil. This could account for the wide scattering of the points. The data of Hebbard and Badger,
218
lNDUSTRIAL AND ENGINEERING CHEMISTRY
for which pure steam was generated, show much less variation. The above correlation would indicate, in the light of Kirkbride's discussion, that the condensate film was always in viscous flow. This is probably true for the upper portion of the tube, where the amount of condensate was small. But for tubes of such lengths as were used in these three investigations, the accumulation of condensate should result in turbulent flow on the lower portion of the tube, even with small values of At,. This offers an explanation for a smaller negative slope of the curve than would be predicted theoretically for viscous flow. Apparently the rate of heat transfer from condensing steam is affected, but not controlled, by turbulence in the condensate film. With sufficiently high values of At,, it is probable that the turbulence in the film would become of increasing importance. However, the data used here are within the range of most commercial operations. From the correlation here developed it would appear advisable to use shorter rather than longer tubes in vertical condensers and evaporators, in so far as heat transfer on the steam side is concerned.
VOL. 31, NO. 2
Nomenclature D
= diameter of tube, ft.
L
length of tube, ft. steam-film temperature difference, O F. weight of condensate per tube, lb./hr. viscosity, lb./(ft.)(hr.). = density, Ib./cu. ft. = latent heat of condensation, B. t. u./lb.
acceleration of gravity, ft./(hr.) (hr.) 8,k 1 steam-film coefficient, B. t. u./(hr.)(sq. ft.)(" F.) = thermal conductivity, B. t. u./(hr.)(sq. F./ft.). ft.)(O
= At, = W = fi = p
X
Literature Cited ( 1 ) Badger, Monrad, and Diamond, IND.ENG.CREM.,22,700(1930). (2) Fragen, doctorate thesis, Univ. Mich., Feb., 1936.
(3) Hebbard and Badger, IND.ENG.CHEM.,Anal. Ed., 5, 359 (1933). (4) Hebbard and Badger, Trans. Am. Inst. Chem. Eng~a.,30, 194 (1933). ( 5 ) Kirkbride, Ibid., 30, 170 (1933). (6) McCormick,Ibid., 30,216 (1933). (7) Stroebe, Baker, and Badger, IND. ENG.CHEM.,31, 200 (1939). November 3, 1938. Preaentad before the meeting of the Amenoan Institute of Chemioal Engineers, Philadelphia, Pa., November 9 to l l v 1938. RmCmIWD
Composition and Drying Rates
of Soybean Oils H. R. ICRAYBILL, A. W. BLEINSMITH, M. H. THORNTON
AND
Purdue University Agricultural Experiment Station, Lafayette, Ind.
Analyses of Soybean Oils and Drying Rates When Mixed with 10 Per Cent of Tung Oil and Driers v
HEN domestic soybean oil was first offered on the American market, much of it was inferior to that imported from the Orient (3, 11). Several explanations were offered to account for this difference. Junker (7) stated that modern methods of expressing remove more of the nonfatty constituents along with the oil than the crude WIanchurian presses. Fickard (11) and Eastman (3) attributed the poorer quality of the domestic oils to inefficient filtering. Gardner (4) found larger amounts of foots in some of the domestic oils, indicating that the oils had not been permitted to settle long enough. The statement has been made frequently that there is a large variation in the drying rates of domestic crude soybean oils. The Detroit Paint and Varnish Club (a) in 1934 concluded that the variations in induction period of crude soybean oils is due to the presence of antioxidants. Treatment of the crude oils with various oxidizing agents reduced the induction period and increased the drying rate of the oils. I n connection with analyses and drying rate determinations made on samples of soybean oil for the Finished Materials Standards Committee of The American Soybean Manufacturers Association in 1935, the drying rates of the oil samples*
W
Eighty-seven samples of commercial soybean oil were collected at intervals of two or three weeks from thirteen different soybean processing plants during the first six months of 1936. These plants represent three processes-expeller, hydraulic, and solvent. Analyses of the oils were made as follows: per cent of foots, per cent of break (Gardner method), per cent of phosphatides, acid number, iodine number, refractive index, and drying time before and after removal of the phosphatides and associated compounds. There was a close correlation between the Gardner break and the percentage of phosphatides of the crude oils a&calculated from the phosphorus content of the oils. There was a correlation between the average phosphatide contents of the samples of oil from the different plants and the drying rates. No correlation was found between the phosphatide content of the crude oils and the drying rates of the oils from which the phosphatides had been removed. The results show that the presence of phosphatides retards the drying rate of the crude oils but that other factors are also involved.
